Stellar Abundances at the Center of Early Type Galaxies with Fine Structure
arxiv(2024)
摘要
Our understanding of early-type galaxies (ETGs) has grown in the past decade
with the advance of full-spectrum fitting techniques used to infer the
properties of the stellar populations that make-up the galaxy. We present ages,
central velocity dispersions, and abundance ratios relative to Fe of C, N, O,
Mg, Si, Ca, Ti, Cr, Mn, Co, Ni, Cu, Sr, Ba, and Eu, derived using full-spectrum
fitting techniques for three ETGs NGC 2865, NGC 3818, and NGC 4915. Each of
these three galaxies were selected because they have optical, disturbed
structures (fine structure) that are linked to major merger events that
occurred 1, 7, and 6 Gyr ago, respectively. Two of the ETGs, NGC 3818 and NGC
4915, show chemical signatures similar to ETGs without fine structure, which is
consistent with a gas-poor merger of elliptical galaxies in which substantial
star formation is not expected. For NGC 2865, we find a statistically higher
abundance of Ca (an α-element) and Cr and Mn (Fe-peak elements). We show
that for NGC 2865, a simple gas-rich merger scenario fails to explain the
larger abundance ratios compared to ETGs without fine structure. These three
early-type galaxies with fine structure exhibit a range of abundances,
suggesting ETGs with fine structure can form via multiple pathways and types of
galaxy mergers.
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